Method of charging temperature



p 2, 1947. J. E. saving 2,426,663

METHOD OF camame TEMPERATURE RESPONSIVE SYSTEMS 2. Sheets-Sheet 1 FiledJune 7, 1943 WEE.

INVENTOR. Be

' I ll AH- rneg J.,E. BEVINS Sept. 2, 1947.

METHOD OF CHARGING TEMPERATURE RESPONSIVE SYSTEMS Filed June '7, 1945 2Sheets-Sheet 2 INVENTOR, 8 1am 85E. Begins.

Af'f'onzey Patented Sept. 2, 1947 METHOD OF CHARGING TEMPERATURERESPONSIYE SYSTEMS James E. Bevins, Hackensack, N. 1., assignor toBendix Aviation Corporation, Bendix, N. J., a

corporation of Delaware Application 'June 7, 1943, Serial No. 489,983

The present invention relates to a method of charging temperatureresponsive systems, and more particularly to an air thermometer usedwith airspeed indicators.

True airspeed indicators are designed to indicate relative velocitybetween the air stream and the craft at any altitude and temperaturelikely to be encountered in normal service. Unless the instrumentincludes a compensator means responsive to the different air densitiespresent at different altitudes and temperatures, the pilot must correctthe indicated airspeed reading in accordance with each variation inaltitude and temperature, as the instrument will not read accuratelywith respect to zero, except for the originally calibrated air densityfrom a given relative altitude and temperature.

To obtain true airspeed at all normally experienced altitudes andtemperatures, prior devices use vapor tension or liquid-filledthermometers requiring two or more Bourdon tubes or diaphragms tocompensate for the pressures created from sudden air density variations.With the air thermometer provided by the present invention, thepressures created by suchchanges in air density are relatively low, ascompared with pressures created in the above prior devices, making itsatisfactory to use one pressure responsivemember to give bothtemperature and altitude correction (density correction).

Accordingly, an object of the invention is to provide a low pressurethermometer adapted to structurally simplify prior art compensatingdevices of the class above referred to. v

Another object of invention'is to provide an improved air thermometercontaining a highly active gas adsorption medium. Another object is toprovide a compensating Bourdon tube or diaphragm with a gaseous mediumand material having adsorbing and diffusing qualities responsive totemperature changes,

and a method of charging the compensating diaphragm with the gaseousmedium.

The above and further objects and advantages of the invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein an airspeed indicator modified by a compensating temperatureresponsive diaphragm is illustrated. It is to be expressly understoodthat the drawings are for purposes of illustration and description onlyand are not designed as a definition of the limits of the invention.

In the drawings, wherein like reference char- 2 Claims. (01. 226-19)acters refer to like parts throughout the several views:

Figure 1 is a perspective view of the accessory unit.

Figure 2 is a longitudinal'cross section view of the casing with theelements inside shown in elevation.

Figure 3 is a transverse view partly in elevation of the casing andelements housed therein, a

section being taken as shown at line 33 in Figure 2. Figure 4= is anenlarged elevational view of one form of mechanical compensator linkage.

Referring in detail to the drawings, I0 is a casing open at the frontprovided with an annular groove ii to receive a snap ring i2 and with anannular shoulder l3 to support ring or frame I4.

The surface of frame I4 is recessed to receive a centrally perforatedplate I! to which is secured a bushing 22 having a coupling flange 23,coupled flush against the under side of plate I! by bolts 20 and 2|.Extending from within the casing i0, through bushing 22, is an indicatorhand spindle 24.

Spindle 24 has the usual indicator hand It on the outer extremity and isin operative mechanical connection at the other end, inside casing in.to diaphragm 25. suspended from apertured lug 26 on shaft 21. ,Shaft 21is held in lug 26 by set screw 28, see Fi ure 3.

Diaphragm 25 is actuated by differential in static and dynamic pressurereceived through static' pressure connection 26a and dynamic pressureconnection 25a coupled to capillary tube 25b, see Figures 2 and 3.

Adjustably pivoted to upstanding lug 24' of diaphragm 25 is a link 29,of a toggle link connection comprising link 29 andlink 20. Link 30 issecured to a yoke 3i, adjustably secured by a set screw 32 to anoscillator bar 33, suitably iournalled in plate l5. Also secured to bar33 is the inner end of back-lash take-up hair spring 32a, with the outerend secured to pin 14a on frame l4. At the opposite end, link 20 isassociated with a common pivot 34 in yoke 35, see Figure 2,eccentrlcally pivoted with rocker bracket 38 having lugs 31 and, pivoted1between axial screw pins 28 and 40 threaded through lugs in frame 4|.

gated split lug 43 clamped thereto by screw 44. Split lug 43 isapertured at the opposite end (see Figure 4) to receive elongated bar45. Bar 45 is adjustably secured lathe-split" lug aperture by set screw46", soethat an' end-protrudes 'there- 1fl-t-fltowhichispivoted'iink;48. a a

Link 48 isadjustably secured te -inwardl tending lug 49 of diaphragm 50by'set' screw 5| 1 andany back-lash in link 48 is taken out by hair 1spring- 31a,-see;1 igure 3. e 1

secured to oscillator bar 33 isa segment'g'ear- 52 so positioned as tomesh with a pinion 53 of subject to the temperature that is to bemeasured. The coil or bulb 55 is completely filled with gas adsorptionmedium, suchas activated coconut charcoal granules 56, before it issoldered to the capillary tubing 54. The system is then completelyevacuated with the bulb 55 at approximately 150 C. It is then chargedwith any suitsystem with a dry gas at substantially sea-level able dry.gas, as carbon dioxide (CO2); During the filling operation, bulb isgradually cooled to the lowest temperature that it is expected toencounter in service, while thefilling gas is still connected to thesystem. The. 3 bulb is next sealed and the gas is in contact with thediaphragm 50 and the activated coconut charcoal in bulb 55 for thepurpose referred under the following heading. Operation Assuming theentire device to be installed in an aircraft, the proximate cause ofcompensation for varying air densities is the reaction of charcoalcontained in bulb 55 with the CO: gas. As

the charcoal is cooled, it adsorbs the gas and causes a partial vacuumin the system. When it is heated, the opposite effect is present andcauses a pressure to expand the-diaphragm 50. This expansion andcontraction of the sensitive element 50 is transmitted through thediflerential 1 linkage to give correct compensation of a True AirspeedIndicator, or to a hand and dial to indicate temperature. Link 48 whendisplaced from a rest position hasthe efifect'of proportionally varyingthe distance between the pivot points of 50 links 29 and 30 at thediaphragm 25 and yoke 3| on oscillaton'bar 33 as long as the pin 34 isnot in line with the axis of pins, and 40, which alignment occurs onlywhen the position of diaphragm 25 indicates zero velocity. This arrange55 ment does not affect the "zero position of pointer l8, but keeps thelinkage set so that, when diaphragm 25 operates, a true indication fromzero results.

' -The characteristics of the system can be conno trolled by making alarger or smaller bulb and 15 As shown in Figuresv land 2, compensatordiacharcoal."-

Any other type "activated carbon can be used to fill such a system,butcoconutj'charcoal satisfactory as iti's-most active forge-sadsorption The'hereindescribed'true airspeed indicator "is claimed inmy. divisional application bearing 1 Serial No.- 612,196'rorAirspeed'indicator, filed on August 23,'1945.

has been illustrated and described, various changes and modifications,which will now appear to those'skilled in the art, may be made-withoutdeparting from the scope of the invention. Ref

erence is therefore to be hadto the appended claimsfor a definition of.the limits of the invention.

What I claimis:

I 1. The method of charging a temperature responsive system including apressure'responsive member and a thermal bulb interconnected by acapillary tube comprising the following steps:-. filling the bulb withcharcoal granules, evacuating air from the system-while heating thevbulb at a predetermined temperature, then filling the pressure whilegradually cooling to the lowest anticipated temperature to beencountered in service and then sealing the system. i

2. The method of charging a temperature re- I 'atapproximately degreescentigrade, then filling the system with carbon dioxide gasatsubstantially sea-level pressure while gradually cooling to the lowestanticipated temperature to be encountered in 'ser'vice'and then sealingthe system; I JAMES E. nnvms. REFERENCES orrnn The following referencesare of record in the file of this, patent: t

" JUNITED STATES PATENTS Number Date I Name 1,272,554 Steenbjerg July16, 1918 1,356,175 Swift ,Oct. 19, 1920 1,615,505 Comman et al.' Jan.25, 1927 2,137,194 Weber Nov. 15, 1938 2,177,244 Ciamberlini Oct. 24,1939 2,302,713 Paulin Nov. 24, 1942 436,045 McElroy Sept. 9, 1890792,588 Fulton June 20,.1905 1,159,893 Browne et a1. -r Nov. 9, 19152,221,633 Dasher. Nov. 12, 1940 2,271,307 Ray Jan. 27, 1942 1,307,037

swe a t vat easem t I While only onebmbodimntcf the invention BristolJune 17,1919.

